NCAA DII and NCAA DIII are proof that the tournaments will still exist even if a division level has no power conferences as members.

Like I said before the power conferences will not sacrifice their other sports, which they have invested time and money in, just to appease their football interests. Do you honestly believe that VT would sacrifice the health of its wrestling, M/W soccer, M/W track and field, baseball, and softball programs just to satisfy some need for football? There are schools (i.e. Michigan) who have more at stake given that the sponsor more non-revenue sports and even invested money build sport specific arenas/stadiums for a few of these sports (i.e. ice hockey, water polo, tennis). So if the power conferences break away, then do you honestly see the ACC, Big XII, Pac-12, and SEC agree to sponsor ice hockey so there are enough participating teams? Do you honestly see the ACC, Big Ten, Big XII, and SEC agree to sponsor M/W water polo so there are enough participating teams? Do you see the Big XII, Pac-12, and SEC agree to sponsor M/W lacrosse so there are enough teams? Here is a break down for some of the sports sponsored at the DI level.

Men's Sports
Football = 130 FBS
Basketball = 351
Baseball = 302
Soccer = 204
Ice Hockey = 59
Lacrosse = 68
Volleyball = 23
Water Polo = 22
Wrestling = 76

Women's Sports
Basketball = 349
Soccer = 333
Volleyball = 334
Softball = 295
Rowing = 88
Lacrosse = 112
Field Hockey = 78
Ice Hockey = 40
Beach Volleyball = 47
Water Polo = 34
Gymnastics = 61

For majority of these sports (maybe even all) the power conferences are in the minority in terms of participating teams. If the power conferences decide to leave for whatever reason, then I guarantee you that the rest of the DI schools will be just fine.